There was once a boy who liked nothing more in the world than to win. He loved winning at whatever it may be: football, cards, video games… everything. And because he couldn't stand losing, he had become an expert in all kinds of tricks and cheating. He could play tricks in practically every situation, without being noticed; even in video games or playing alone. He could win without ever being caught. He won so many times that everyone saw him as the champion. It meant that almost no one wanted to play with him, he was just too far ahead of everyone. One person who did play with him was a poor boy, who was a bit younger. The champion really enjoyed himself at the poor boy's expense, always making the boy look ridiculous. But the champion ended up getting bored with all this. He needed something more, so he decided to apply for the national video games championship, where he would find some competitors worthy of himself. At the championship he was keen to show his skills but, when he tried using all those tricks and cheats he knew from a thousand different games, well… none of them worked. The competition judges had prevented any of the tricks from working. He felt terribly embarrassed: he was a good player, but without his cheats, he couldn't beat a single competitor. He was soon eliminated, and sat there, sad and pensive. Finally, they announced the name of the tournament champion. It was the poor boy from home. The one he had always beaten! Our boy realised that the poor boy had been much cleverer than himself. It hadn't mattered to the poor boy if he lost and got a good beating, because what he was really doing was learning from each of his defeats. And from so much learning he had been transformed into a real master. From then on, the boy who had loved winning gave up wanting to win all the time. He was quite happy to lose sometimes, because that was when he would learn how to win on the really important occasions. 
The desire to always win at everything, to the extent of resorting to cheating, is the greatest obstacle to winning when winning is most important. 